Synthesis and characterization of magnesium-carbon compounds for hydrogen storage

Magnesium (Mg) and carbon (C) compounds were synthesized by ball-milling a mixture of Mg and different graphites with different crystallinities. The materials were characterized by X-ray diffraction, X-ray absorption spectroscopy, and X-ray total scattering techniques. Hydrogen storage properties were also investigated. In the case of the material using low-crystalline graphite, a Mg and C compound was formed as main phase, and its chemical bonding state was similar to that of magnesium carbide (Mg2C3). The hydrogen absorption reaction of the Mg-C compound occurred at around 400 degrees C under 3 MPa of hydrogen pressure to form magnesium hydride (MgH2) and the C-H bonds in the carbon material. The hydrogenated Mg-C material desorbed about 3.7 mass% of hydrogen below 420 degrees C with two processes, which were the decomposition of MgH2 and the subsequent reaction of the generated Mg and the C-H bonds. From the results, it is concluded that the Mg-C compound absorb and desorb about 3.7 mass% of hydrogen below 420 degrees C. (C) 2013 Elsevier Ltd. All rights reserved.